MUSE

Multi Unit Spectroscopic Explorer

Looking like a machine straight out of the movie The Matrix, with its Medusa-like hoses and connections, MUSE is the latest of the second-generation instruments to be installed on Yepun (UT4), the fourth Unit Telescope of the Very Large Telescope at the Paranal Observatory.

Like SINFONI, MUSE is an integral field spectrograph (IFS). An IFS allows you to observe the entirety of an astronomical object in one go, and for each pixel measures the intensity of the light as a function of its colour, or wavelength. The resulting data is a 3D set where each pixel of the image has a full spectrum of the light. MUSE splits the field of view into 24 individual image segments or channels which are each split further into 48 slices or “mini slits”, giving a total of 1152 mini slits. Each set of 48 mini slits is injected into a spectrograph, which disperses the light into its constituent colours, and MUSE measures over 4000 of these colours! From this, the 3D image is created.

“MUSE has been built with the intention of studying the content and processes going on in the very early Universe, when the first stars and galaxies were forming,” explains Fernando Selman, Instrument Scientist for MUSE. “Closer in time and space, MUSE will map the dark matter distribution in clusters of galaxies using the gravitational microlensing effect on background galaxies.” MUSE will also provide detailed information about the internal dynamics of many classes of galaxies with unprecedented detail. “It has already been used to study the Sombrero Galaxy in Virgo, and, in the same cluster, a recently discovered new type of object — a galaxy being destroyed after falling into the cluster and encountering the cluster’s hot gaseous corona,” continues Fernando. An image of this galaxy is shown on this page. The stars themselves found within bigger objects will also be a focus of study — impressive vistas of the Tarantula Nebula and its huge collection of massive young stars have been obtained during the testing phase, and an enormous mosaic of the Orion Nebula has been produced.

With nearly 400 million pixels to be processed in real time, MUSE has presented Paranal Observatory with new computation and communication challenges. During the first phase of commissioning alone, nearly half a billion spectra were produced!

MUSE and adaptive optics

MUSE entered a new era in 2017 with the advanced capabilities of the Adaptive Optics Facility (AOF).
The AOF with Artificial laser stars (4LGSF); deformable active mirrors (ann16078); multiple wavefront sensors GALACSI will develop the full potential of MUSE and is comparable to moving the telescope 900 metres above the Paranal summit, a height free of the effects of the most turbulent layers of the atmosphere, giving much clearer images than before.

MUSE was will be the first of the VLT’s second generation instruments to taste these new capabilities. The module GALACSI will routinely deliver images to MUSE at optical wavelengths of a quality that was previously possible only on the few clearest nights of the year if at all.

“MUSE with the AOF system will allow for the completion of surveys of the remote Universe with unique sensitivity, permitting studies of the earliest galaxies and large scale structures,” says Selman. “During its lifetime we expect many great contributions from this instrument for a wide range of astronomical investigations".

Science highlights with MUSE

Plenty to come! The instrument had just been installed at the telescope when this page was written.